Recently, image digital processing techniques have increasingly been applied to practical use. In general, digitization of video signals results in an enormous amount of information, and hence such information is difficult to transmit or record without compression in terms of communication rate, cost, and the like. Image compression techniques are indispensable for, for example, transmitting or recording digital video signals; various standardization techniques have been examined and put into practice. As techniques for moving pictures, MPEG (Moving Picture Experts Group) schemes have been standardized.
The MPEG-2 scheme, in particular, has become most popular as a standardization scheme for image compression, and are used for digital TV broadcasts in the USA, Europe, and Japan. In addition, with advances in digitization and image compression techniques, deterioration in transmission and recording can be reduced, and high-quality playback images can be obtained.
As digitization techniques advance as described above, with regard to TV broadcasts, multi-channel broadcasts realized by effectively using frequency bands, e.g., satellite digital TV broadcast services, are expected in place of analog broadcasts. With the popularization of digital TV broadcasts, there may be cases where broadcast signals are recorded, and the recorded signals are played back at desired points of time, thereby allowing users to watch programs at the desired times. In this case, a function and device which receive digital broadcast signals and directly record them are required.
In general, however, a digital TV broadcast receiving apparatus having a digital broadcast signal recording function of this type has only one tuner unit. For this reason, with regard to programs on channels which are modulated with the same RF and transmitted, this apparatus can display a program on a given channel in real time, and at the same time, can record a program on another channel to allow a user to playback the recorded program afterward so as to display and watch it. However, with regard to programs on two channels which are modulated with different RFs (e.g., different modulation frequencies are used depending on transponders in the case of satellite digital TV broadcasts) and transmitted, the apparatus cannot simultaneously display a program on one channel in real time and record a program on the other channel to allow the user to playback the recorded program afterward so as to display and watch it.
Such a problem can be simply solved by providing a plurality of tuner units for a receiving apparatus. However, it is not desirable to provide a plurality of tuner units for one digital TV broadcast receiving apparatus with a digital broadcast signal recording function from the viewpoint of increases in the cost and volume of the apparatus.